Use zcash_script in PCZTs

This replaces the local script implementation with the one from the
zcash_script crate.

The `Script` type that was here is replaced by a family of three types
- `script::PubKey`;
- `script::Sig<PushValue>` – a v5+ script_sig, used for new sigs;
- `script::Sig<Opcode>` – a pre-v5 script\_sig, used for sigs read off
  the chain, which may predate NU5; and
- an unwrapped `Vec<u8>` for script code.

This uses a number of zcash_script features that haven’t yet made it
into the master branch, let alone a release, so this should not be
merged.

Cargo.toml

@@ -43,6 +43,7 @@ zip321 = { version = "0.3", path = "components/zip321" }
 zcash_note_encryption = "0.4.1"
 zcash_primitives = { version = "0.22", path = "zcash_primitives", default-features = false }
 zcash_proofs = { version = "0.22", path = "zcash_proofs", default-features = false }
+zcash_script = "0.2.0"
 
 pczt = { version = "0.2", path = "pczt" }
 
@@ -209,3 +210,6 @@ debug = true
 
 [workspace.lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(zcash_unstable, values("zfuture"))'] }
+
+[patch.crates-io]
+zcash_script = { git = "https://github.com/ZcashFoundation/zcash_script.git", rev = "d0365cd7d75ca45c4595af09d9732146e6132fb2" }

pczt/Cargo.toml

@@ -14,6 +14,7 @@ categories.workspace = true
 zcash_note_encryption = { workspace = true, optional = true }
 zcash_primitives = { workspace = true, optional = true }
 zcash_protocol = { workspace = true, optional = true }
+zcash_script.workspace = true
 
 blake2b_simd = { workspace = true, optional = true }
 rand_core = { workspace = true, optional = true }

pczt/src/transparent.rs

@@ -12,6 +12,8 @@ use getset::Getters;
 use serde::{Deserialize, Serialize};
 use serde_with::serde_as;
 
+use zcash_script::{opcode::PushValue, script};
+
 /// PCZT fields that are specific to producing the transaction's transparent bundle (if
 /// any).
 #[derive(Clone, Debug, Serialize, Deserialize, Getters)]
@@ -61,19 +63,19 @@ pub struct Input {
     /// A satisfying witness for the `script_pubkey` of the input being spent.
     ///
     /// This is set by the Spend Finalizer.
-    pub(crate) script_sig: Option<Vec<u8>>,
+    pub(crate) script_sig: Option<script::Sig<PushValue>>,
 
     // These are required by the Transaction Extractor, to derive the shielded sighash
     // needed for computing the binding signatures.
     #[getset(get = "pub")]
     pub(crate) value: u64,
     #[getset(get = "pub")]
-    pub(crate) script_pubkey: Vec<u8>,
+    pub(crate) script_pubkey: script::PubKey,
 
     /// The script required to spend this output, if it is P2SH.
     ///
     /// Set to `None` if this is a P2PKH output.
-    pub(crate) redeem_script: Option<Vec<u8>>,
+    pub(crate) redeem_script: Option<script::PubKey>,
 
     /// A map from a pubkey to a signature created by it.
     ///

zcash_client_backend/Cargo.toml

@@ -31,6 +31,7 @@ zcash_keys = { workspace = true, features = ["sapling"] }
 zcash_note_encryption.workspace = true
 zcash_primitives = { workspace = true, features = ["std", "circuits"] }
 zcash_protocol.workspace = true
+zcash_script.workspace = true
 zip32.workspace = true
 zip321.workspace = true
 transparent.workspace = true